Connection of modular high-voltage electrical equipment having a metallic envelope by insulated connections is a technique that is becoming widespread among the various manufacturers of electrical equipment.
These coupling systems can be classified into two groups:
Coupling systems in which the union of the equipment is achieved by a connector or connection assembly comprising an insulating piece or envelope, generally a body of revolution, inside which are the conducting elements. In this kind of systems the ends of the insulating piece penetrate the corresponding female connectors mounted on the equipment to be connected, electrically sealing the union. Examples of coupling systems of this kind are described for example in the following Patents: EP 0 520 933, WO 02/087042, WO 02/35668, EP 0 891 013 and DE 10119183.
Coupling systems in which the insulating element does not penetrate the pieces provided in the equipment to be joined electrically. Examples of these designs are described in European Patents 1 294 064 and 0 199 208. In these cases, in order to ensure the seal from an electrical standpoint, compression rings may be used as shown in European Patent 1 294 064.
In these coupling systems in order to control the distribution of the electric field in all cleanliness and humidity conditions, the surface of the connector or union assembly exposed between the two high-voltage equipment is referred to the ground potential, for which said external surface must be conducting or semi-conducting. For this purpose, it is common to use semi-conducting paint or semi-conducting materials injected on the insulating piece or envelope.
In order to provide the ground potential to said semi-conducting surface, helical springs may be used attached or connected on one end to the metallic envelope of the high-voltage electrical equipment, which is connected to earth, and on the other end are in contact with the semi-conducting layer of the connector or union assembly. The contact between the spring and the semi-conducting surface may be effected in two ways:
Tangential.
In this case the spring, disposed linearly, is attached by both ends to the metallic envelope of the high-voltage equipment. Contact with the semi-conducting surface is achieved by placing said surface between the two attachments of the spring, forcing the latter to deform into an arc instead of following a straight line between the attachments, thereby ensuring a permanent contact.
Circular.
In this case the spring, electrically connected to earth, forms a torus about the semi-conducting surface, such as shown in patent application DE 10119183.
This manner of providing the ground potential to the external semi-conducting layer of the connector or union assembly has the disadvantage that an excessive and prolonged vibration during transport of the equipment may wear the semi-conducting paint due to rubbing against the spring, producing surface areas without potential that could cause a dielectric failure resulting in an arc of a short but undefined length.
Another problem that may occur in these coupling systems between electrical equipment is penetration by pointed objects in the interstices between the equipment, damaging the exposed part of the connector or union assembly.
In addition, the need to monitor and automate electrical installations requires placing between the electrical equipment corresponding voltage and current sensors or gauges which, in the case of coupling between high-voltage cells, implies an additional difficulty as it requires making modifications in the high-voltage cells to allow making the required measurements.
Determining the presence of a voltage in the busbars of the main circuit of a set of high-voltage cells can be solved by using devices for insulated connections such as those disclosed in International application WO 02/35668, but the problem is that the high-voltage cells are not always installed with female connectors on the free side that allow using the device described in said patent application, and in any case it is not possible to measure the circuit current at the end of the set of cells.